Large Separation Research Articles

Deep imaging of three accelerating stars using SHARK-NIR and LMIRCam at LBT

Abstract The combination of detection techniques enhances our ability to identify companions orbiting nearby stars. We employed high-contrast imaging to constrain mass and separation of possible companions responsible for the significant proper motion anomalies of the nearby stars HIP 11696, HIP 47110 and HIP 36277. These targets were observed using the LBT’s high-contrast camera, SHARK-NIR, in H-band using a Gaussian coronagraph, and with the LMIRCam instrument in the L’-band and using a vAPP coronagraph. Both observations were conducted simultaneously. Additionally, constraints at short separations from the host star are derived analyzing the renormalized unit weight error (RUWE) values from the Gaia catalogue. We find that the companion responsible for the anomaly signal of HIP 11696 is likely positioned at a distance from 2.5 to 28 astronomical units from its host. Its mass is estimated to be between 4 and 16 Jupiter masses, with the greater mass possible only at the upper end of the separation range. Similar limits were obtained for HIP 47110 where the companion should reside between 3 and 30 au with a mass between 3 and 10 MJup. For HIP 36277, we identified a faint stellar companion at large separation, though it might be substellar depending on the assumed age for the star. Considering the older age, this object accounts for the absolute value of the PMa vector but not for its direction. Additionally, we found a substellar candidate companion at a closer separation that could explain the PMa signal, considering a younger age for the system.

Measurement of boosted Higgs bosons produced via vector boson fusion or gluon fusion in the H →bb¯ decay mode using LHC proton-proton collision data at s = 13 TeV

A measurement is performed of Higgs bosons produced with high transverse momentum (pT) via vector boson or gluon fusion in proton-proton collisions. The result is based on a data set with a center-of-mass energy of 13 TeV collected in 2016–2018 with the CMS detector at the LHC and corresponds to an integrated luminosity of 138 fb−1. The decay of a high-pT Higgs boson to a boosted bottom quark-antiquark pair is selected using large-radius jets and employing jet substructure and heavy-flavor taggers based on machine learning techniques. Independent regions targeting the vector boson and gluon fusion mechanisms are defined based on the topology of two quark-initiated jets with large pseudorapidity separation. The signal strengths for both processes are extracted simultaneously by performing a maximum likelihood fit to data in the large-radius jet mass distribution. The observed signal strengths relative to the standard model expectation are 4.9−1.6+1.9 and 1.6−1.5+1.7 for the vector boson and gluon fusion mechanisms, respectively. A differential cross section measurement is also reported in the simplified template cross section framework.

Design of Two-Dimensional Hybrid Perovskites with Giant Spin Splitting and Persistent Spin Textures.

Semiconductors with large energetic separation ΔE± of energy sub-bands with distinct spin expectation values (spin textures) represent a key target to enable control over spin transport and spin-optoelectronic properties. While the paradigmatic case of symmetry-dictated Rashba spin splitting and associated spin textures remains the most explored pathway toward designing future spin-transport-based quantum information technologies, controlling spin physics beyond the Rashba paradigm by accessing strategically targeted crystalline symmetries holds significant promise. In this paper, we show how breaking the traditional paradigm of octahedron-rotation based structure distortions in 2D organic-inorganic perovskites (2D-OIPs) can facilitate exceptionally large spin splittings (ΔE± > 400 meV) and spin textures with extremely short spin helix lengths (lPSH ∼ 5 nm). A simple bond angle difference captures the distortion-driven global asymmetry and correlates quantitatively with first-principles computed spin-splitting magnitudes. A multiband effective mass model that accounts for interlayer coupling provides a unified understanding of how specific symmetry elements dictate layer- and state-dependent spin polarizations within these multi-quantum-well structures. The general symmetry analysis methodology presented here, together with the potential for rationally creating 2D-OIPs with unique symmetry patterns, opens a pathway to design semiconductors with outstanding spin properties for next generation opto-spintronics.

Energy-momentum correlators of fermions at finite temperature and density

Equal-time commutators of different components of the energy-momentum tensor at spatially separated points are calculated for a relativistic quantum Fermi gas at finite temperature and density. Different definitions of such components, also known as different pseudogauges, are used and smeared with a Gaussian profile characterized by the width σ. In this way, we introduce observables that may represent measurements of energy and momentum in a spatial region of size σ. We find that the obtained commutators are sensitive to the pseudogauge chosen if the probed systems or the spatial separation are small. The pseudogauge dependence is expected as different quantum operators are analyzed in this case. On the other hand, we find that for sufficiently large probed systems or with large separation, the studied commutators are pseudogauge independent. Published by the American Physical Society 2024

Numerical Study of Supersonic Cavity Flows with Different Turbulent Models

A numerical study of supersonic cavity flows is conducted with different turbulent models, including RANS, LES, DES, DDES, and IDDES. Firstly, a supersonic cavity-ramp flow with Ma∞ = 2.92 is simulated numerically. It shows that the results of DDES and IDDES are nearly equivalent. The wall skin-friction coefficients obtained by these two models are in better agreement with the experimental measurement than those of DES. The reason is that the RANS region of DDES and IDDES is larger than that of DES, so it produces more turbulence in the near-wall region. In comparison, RANS cannot accurately predict large separation flows. The shear layer’s reattachment point on the ramp predicted by RANS is biased downstream compared to the experimental measurement, making its overall prediction accuracy worse than other models. The results obtained by LES are comparable to those obtained by DDES and IDDES except for the wall skin-friction coefficient, which is much smaller because the grid resolution is not high enough to accurately resolve the near-wall turbulent flow. Secondly, the effect of different aft-wall angles (θ) on the flow characteristics of the supersonic cavity is investigated numerically with IDDES. We find that as θ decreases, the oscillation intensity of the cavity flow continuously decreases. However, the change in cavity drag with θ is non-monotonic, which means that there might be a critical θ at which the drag penalties of a cavity are minimal. Therefore, an optimal design should be achieved when changing θ to control the oscillation intensity of supersonic cavity flows.

Optimal Floquet state engineering for large scale atom interferometers

The effective control of atomic coherence with cold atoms has made atom interferometry an essential tool for quantum sensors and precision measurements. The performance of these interferometers is closely related to the operation of large wave packet separations. We present here a novel approach for atomic beam splitters based on the stroboscopic stabilization of quantum states in an accelerated optical lattice. The corresponding Floquet state is generated by optimal control protocols. In this way, we demonstrate an unprecedented Large Momentum Transfer (LMT) interferometer, with a momentum separation of 600 photon recoils (600 ℏk) between its two arms. Each LMT beam splitter is realized in a remarkably short time (2 ms) and is highly robust against the initial velocity dispersion of the wave packet and lattice depth fluctuations. Our study shows that Floquet engineering is a promising tool for exploring new frontiers in quantum physics at large scales, with applications in quantum sensing and testing fundamental physics.

Parameter Estimation and Identifiability in Kinetic Flux Profiling Models of Metabolism

Metabolic fluxes are the rates of life-sustaining chemical reactions within a cell and metabolites are the components. Determining the changes in these fluxes is crucial to understanding diseases with metabolic causes and consequences. Kinetic flux profiling (KFP) is a method for estimating flux that utilizes data from isotope tracing experiments. In these experiments, the isotope-labeled nutrient is metabolized through a pathway and integrated into the downstream metabolite pools. Measurements of proportion labeled for each metabolite in the pathway are taken at multiple time points and used to fit an ordinary differential equations model with fluxes as parameters. We begin by generalizing the process of converting diagrams of metabolic pathways into mathematical models composed of differential equations and algebraic constraints. The scaled differential equations for proportions of unlabeled metabolite contain parameters related to the metabolic fluxes in the pathway. We investigate flux parameter identifiability given data collected only at the steady state of the differential equation. Next, we give criteria for valid parameter estimations in the case of a large separation of timescales with fast–slow analysis. Bayesian parameter estimation on simulated data from KFP experiments containing both irreversible and reversible reactions illustrates the accuracy and reliability of flux estimations. These analyses provide constraints that serve as guidelines for the design of KFP experiments to estimate metabolic fluxes.

Novel metal-organic framework hydrogel for enhanced selective removal of uranyl ions from nuclear wastewater

The efficient removal of uranium (U(Ⅵ)) from nuclear wastewater presents a significant challenge due to the high concentrations of uranium and various interfering ions. In this study, we developed and used metal-organic framework hydrogel (MOFH) as a highly efficient adsorbent for uranium removal. The MOFH, synthesized with ferrocyanides and functional groups (Fe(Ⅱ)-CN-Fe(Ⅲ), OH, -COOH, and -NH2), exhibited good chemical stability, large separation capacity, and high selectivity. The hydrogel's three-dimensional network, crosslinked with chitosan and alginic acid, significantly enhanced uranium removal. Even in the presence of high concentrations of coexisting cations and organic matter, the MOFH maintained a high removal rate (>95%) and distribution coefficient (Kd), and thus demonstrated strong resistance to interference from coexisting ions and showed great applicability in complex wastewater. The study also explored the MOFH's potential in treating uranium-contaminated wastewater from a smelting mine, showing effective uranium removal with minimal impact on other wastewater components. This research contributes to the development of novel adsorption materials and the understanding of their removal mechanisms, offering a comprehensive solution for the efficient removal of uranium from aqueous systems.

Molecular engineering in thizolo[5,4-d]thiazole-based donor-acceptor covalent organic framework Induced high-efficient photosynthesis of H2O2

Covalent organic frameworks (COFs), as a newly emerging kind of porous and crystalline materials, serve as an ideal template for hydrogen peroxide (H2O2) photosynthesis. However, the vision of achieving high efficiency and selectivity in H2O2 photosynthesis is greatly hindered by the large exciton binding energy and limited charge separation efficiency influenced by the molecular structure of the building blocks. Herein, we developed three newly designed COFs with a donor–acceptor (D-A) structure and incorporated regulatory units (fluorine, F, and methoxyl, OCH3) in the D-A pathway through molecular engineering to optimize electronic structure, the availability of activate sites, charge kinetics and O2 activation capacity. Due to electron-donating effect, OCH3-functionalization (NIES-COF-3) can strengthen the intramolecular electron transfer and interaction with O2. This results in a reduction of the energy barrier of the rate-determining step (*O2 → *OOH) and excellent O2-to-H2O2 photocatalytic activity under visible light irradiation, delivering an H2O2 production rate of 3238.4 μmol g−1h−1 and a high apparent quantum yield of 3.17 %. In addition, F-functionalization (NIES-COF-2) primarily reduces the band-gap energy and improve the O2 adsorption capacity compared to unfunctionalized NIES-COF-1. This work unveils insight into the catalytic activity-optimization mechanism of molecular engineering in the D-A structure and provides important references for photocatalysts.

Influences in Experimental Studies on the Characteristics of Transonic Shock Buffet

This article examines the evolution of transonic shock buffet on the OAT15A supercritial airfoil, aspiring to elucidate some of the causes of disparate buffet-relevant settings reported in the literature. Experimental campaigns on three distinct chord lengths are conducted thus resulting in chord Reynolds numbers of 1.3×106, 2.0×106, and 2.7×106. Continuous variations in Mach and AoA allow mapping the shock wave behavior across a large parameter space and capturing the transition between prebuffet, onset, developed buffet, and offset. High-speed focusing schlieren imaging is employed to extract the temporal and spectral nature of buffet and to deduce key quantities that characterize the unsteadiness. Three-dimensional effects along the span due to interference with the side walls are assessed thoroughly, revealing that phases of upstream shock motion and large separation are accompanied by 3D distortion. Even though this effect gains relevance at reduced aspect ratio, a substantially 2D character of the shock surface around the centerplane is confirmed. Fully developed buffet governed by a 2D buffet mode is proven to exist across all test cases, although the buffet peak condition is gradually shifted toward reduced angle of attack, yet greater Mach number with increased Reynolds number. Conversely, accompanied by severely increased angles of attack, the buffet mechanism appears more volatile for small chord length and is consolidated with enlarged chord, which strongly suggests a dependence on the state of the turbulent boundary layer.

Highly separated transitional shock-wave/boundary-layer interactions: A spatial modal study

At cruise altitudes, the Reynolds number may become sufficiently low to allow a laminar boundary layer to persist on the suction side of a transonic fan blade up to the shock-wave/boundary-layer interaction (SBLI). In such a transitional SBLI with sufficiently large shock-induced separation, a shock oscillation mechanism occurs, with the source at the upstream growth (until a critical length) and natural suppression (through shear layer instabilities) of the separation bubble. The oscillation cycle is characterized by a temporarily vanishing upstream laminar part of the separation bubble. The suppression of this laminar part is accompanied by downstream advection of turbulence and subsequent entrainment into the bulk separation bubble, affecting the reflected shock movement. In order to study the spatial behavior of the mechanism, particle image velocimetry of a highly separated transitional oblique SBLI at Mach 2.3 is conducted in the high speed aerodynamics laboratory of Delft University of Technology. Statistical quantities, including root mean square velocity fluctuations, phase averages, and spatial modes from proper orthogonal decomposition, are investigated. The entrainment strength varies depending on the phase of the oscillation, and the turbulent shear layer is not fully developed. The main growth and shrinking mode of the separation bubble were extracted, which affects the slip line region size and shock position. Secondary modes that affect the shear layer undulation and upstream effects were also extracted. The study provides quantitative analyses of an important shock oscillation type, with the focus on capturing the separation bubble size variation and upstream effects.

Numerical assessment of ice formation processes and its impact on a variable-pitch unmanned aerial vehicles propeller in forward flight

Unmanned aerial vehicles (UAVs) encounter significant challenges in freezing climates, as atmospheric ice accretion adversely impacts both flight safety and aerodynamic performance. This study provides an in-depth numerical investigation into the ice accretion process and its implications on the aerodynamic performance of UAV propeller. The analysis explores at various propeller blade pitching angles and rotational speeds. Detailed flow field analysis around propeller blade surfaces is conducted to address the performance degradations associated with ice accretion. The investigation reveals a noteworthy shift in ice shapes and extents with varying pitching angles and rotational speeds. The iced propeller demonstrates increased aerodynamic losses, marked by large size separation bubbles aft the ice shapes at outer radial locations. Remarkably, at higher pitching angles, the iced propeller outperforms the baseline propeller, followed by a propeller with increased rotating speed. For both baseline and higher pitching angles, the most significant losses in thrust coefficient 57.60% and 25.39%, respectively, occur at −2 °C, accompanied by maximum spikes in power coefficient of 140.08% and 93.92% at −4 °C. Meanwhile, an increase in rotating speed results in a decrease in thrust coefficient by 48.60% and an increase in power coefficient by 150.66% at an icing temperature of −4 °C.

Shock Oscillation Mechanism of Highly Separated Transitional Shock-Wave/Boundary-Layer Interactions

Reynolds numbers at cruise altitude can be such that a laminar boundary layer persists on the suction side of a transonic fan blade up to the shock-wave/boundary-layer interaction (SBLI). In a transitional SBLI which exhibits sufficiently large shock-induced separation, a shock oscillation mechanism characterized by growth and natural suppression of the upstream laminar section of the separation bubble occurs. To validate the shock oscillation mechanism observed in large eddy simulations (LES), the shock oscillation mechanism is studied experimentally using high-speed Schlieren and spark-light shadowgraphy. A characteristic length based on the distance of laminar separation shock travel is proposed. Strouhal numbers from LES and the experiment collapse at around 0.075. A strong dependency of the oscillation mechanism on free-stream turbulence and boundary-layer state is shown. Dominant oscillation frequencies are an order of magnitude lower for the turbulent interaction as opposed to the laminar case. For the laminar case, dynamic mode decomposition showed a strong relationship of the laminar separation shock with the separation bubble and reflected shock movement. The turbulent interaction shows a significantly lower reflected shock travel distance. The findings experimentally confirm that stabilization of the shock is achieved by tripping the boundary layer.

Joint Observation of a Series of Magnetic Holes by Tianwen-1 and MAVEN on Mars

Magnetic holes (MHs) are transient magnetic structures responsible for energy conversion in space plasma. Using single-spacecraft measurements from Mars Atmosphere and Volatile EvolutioN (MAVEN), the existence of MHs on Mars has been confirmed. However, due to the limitations of single-spacecraft observations, significant uncertainty also arises on the identification of the spatial scale and 3D geometry of MHs. In this study, we report a series of MHs successively detected by Tianwen-1 near the high-latitude magnetopause and by the MAVEN spacecraft near the subsolar magnetopause. The large separation between Tianwen-1 and MAVEN (∼4 R M) suggests these MHs are macroscale structures extending along the axial direction. Additionally, we observe whistler waves generated by electron perpendicular anisotropy in one of the macroscale MHs. This study is the first joint observation of Martian MHs, shedding light on the research of transient magnetic structures on Mars.

KIC 8840638: A Newly Discovered Eclipsing Binary with δ Scuti–Type Oscillations

In this paper, we analyze the light variation of KIC 8840638 using high-precision time-series data from the Kepler mission. The analysis reveals that this target is a new detached eclipsing binary system with a δ Scuti component, rather than a single δ Scuti star as previously known. The frequency analysis of short-cadence data reveals 95 significant frequencies, most of which lie in a frequency range of 23−32 day−1. Among them, seven independent frequencies are detected in the typical frequency range of δ Scuti stars, and they are identified as pressure modes. In addition, a possible large separation value of Δν = 36.5 ± 0.1 μHz is also detected with the Fourier transform (FT) and autocorrelation function (AC) analysis. The orbital frequency f orb (= 0.320008 day−1) and its harmonics are also detected directly in the frequency spectrum. The binary modelings derived from PHOEBE indicate that this binary system is in detached configurations with a mass ratio of q=0.33−0.04+0.06 , an inclination angle of 40.19−2.84+3.96 ​​​​​°. The derived parameters and binary evolutionary model suggest that the primary star is an object on the verge of leaving the main sequence with a temperature of ∼7600 K, while the secondary appears to be a cool component entering the giant branch with a temperature ∼3100 K lower than the primary. Moreover, this system may have undergone a mass ratio reversal, where the more massive star is the gainer component and the less massive one is the donor star.

SPH modelling of AGB wind morphology in hierarchical triple systems and a comparison to observation of R Aql

Context. Complex asymmetric 3D structures are observed in the outflows of evolved low- and intermediate-mass stars, and are believed to be shaped through the interaction of companions that remain hidden within the dense wind. One example is the AGB star R Aql, for which ALMA (Atacama Large Millimeter Array) observations have revealed complex wind structures that might originate from a higher-order stellar system. Aims. We investigate how triple systems can shape the outflow of asymptotic giant branch (AGB) stars and characterise the different wind structures that form. For simplicity, we solely focus on co-planar systems in a hierarchical, stable orbit, consisting of an AGB star with one relatively close companion, and another one at a large orbital separation. Methods. We modelled a grid of hierarchical triple systems including a wind-launching AGB star, with the smoothed-particle- hydrodynamic PHANTOM code. We varied the outer companion mass, the AGB wind velocity, and the orbital eccentricities to study the impact of these parameters on the wind morphology. To study the impact of adding a triple companion, we additionally modelled and analysed a small grid of binary sub-systems, for comparison. To investigate if R Aql could be shaped by a triple system, we postprocessed one of our triple models with a radiative transfer routine, and compared this to data of the ALMA ATOMIUM programme. Results. The characteristic wind structures resulting from a hierarchical triple system are the following. A large two-edged spiral wake results behind the outer companion star. This structure lies on top of the spiral structure formed by the close binary, which is itself affected by the orbital motion around the system’s centre of mass, such that it resembles a snail-shell pattern. This dense inner spiral pattern interacts with, and strongly impacts, the spiral wake of the outer companion, resulting in a wave pattern on the outer edge of this spiral wake. The higher the mass of the outer companion, the larger the density enhancement and the more radially compressed the outer spiral. Lowering the wind velocity has a similar effect, and additionally results in an elongation of the global wind morphology. Introducing eccentricity in the inner and outer orbit of the hierarchical system results in complex phase-dependent wind-companion interactions, and consequently in asymmetries in the inner part of the wind and the global morphology, respectively. From the comparison of our models to the observations of R Aql, we conclude that this circumstellar environment might be shaped by a similar system to the ones modelled in this work, but an elaborate study of the observational data is needed to better determine the orbital parameters and characteristics of the central system. Conclusions. The modelled outflow of an AGB star in a co-planar hierarchical systems is characterised by a large-scale spiral wake with a wavey outer edge, attached to the outer companion, on top of a compact inner spiral pattern that resembles a snail-shell pattern.

Analytical Second-Order Extended Kalman Filter for Satellite Relative Orbit Estimation

This study considers a relative orbit estimation problem wherein an observing spacecraft navigates with respect to a target space object at a large separation distance (several kilometers) using only the bearing angles obtained by a single onboard camera. Generally, the extended Kalman filter (EKF), which is based on linear relative motion equations such as the Clohessy–Wiltshire equation, is used for the relative navigation of satellites. The EKF linearizes the estimation error around the current estimate and applies the Kalman filter equations to this linearized system. However, it has been shown that nonlinearities of the orbit determination problem can make the linearization assumption insufficient to represent the actual uncertainty. Therefore, an analytical second-order extended Kalman filter (ASEKF) for relative orbit estimation is proposed in this study. The ASEKF, to sequentially estimate the relative states of satellites and their associated uncertainties, is formulated based on a second-order analytic relative-motion equation under J2-perturbtation, which can overcome the deficiencies of existing approaches that mainly focus on applications in two-body, near-circular, and linearized orbit dynamics. Numerical results show that the proposed method provides superior robustness and mean-square error performance compared to linear estimators under the conditions considered.

Hydrodynamic shielding in radiative multicloud outflows within multiphase galactic winds

ABSTRACT Stellar-driven galactic winds regulate the mass and energy content of star-forming galaxies. Emission- and absorption-line spectroscopy show that these outflows are multiphase and comprised of dense gas clouds embedded in much hotter winds. Explaining the presence of cold gas in such environments is a challenging endeavour that requires numerical modelling. In this paper, we report a set of 3D hydrodynamical simulations of supersonic winds interacting with radiative and adiabatic multicloud systems, in which clouds are placed along a stream and separated by different distances. As a complement to previous adiabatic, subsonic studies, we demonstrate that hydrodynamic shielding is also triggered in supersonic winds and operates differently in adiabatic and radiative regimes. We find that the condensation of warm, mixed gas in between clouds facilitates hydrodynamic shielding by replenishing dense gas along the stream, provided that its cooling length is shorter than the cloud radius. Small separation distances between clouds also favour hydrodynamic shielding by reducing drag forces and the extent of the mixing region around the clouds. In contrast, large separation distances promote mixing and dense-gas destruction via dynamical instabilities. The transition between shielding and no-shielding scenarios across different cloud separation distances is smooth in radiative supersonic models, as opposed to their adiabatic counterparts for which clouds need to be in close proximity. Overall, hydrodynamic shielding and re-condensation are effective mechanisms for preserving cold gas in multiphase flows for several cloud-crushing times, and thus can help understand cold gas survival in galactic winds.

Numerical analysis of the fungibility of disclination dipole by dislocation array or dislocation monopole

Disclinations have been discovered and applied to a wide variety of materials, underscoring the importance of their analysis. Previous studies have demonstrated that a disclination dipole can be represented by a dislocation array in a deformation schematic and by a dislocation monopole in a stress state. Based on these observations, we propose that the elastic field of a disclination dipole can be substituted with that of a dislocation array or dislocation monopole, allowing the development of the disclination theory grounded in dislocation theory. In this study, we conducted a quantitative analysis of the elastic strain–energy of disclination dipoles, dislocation arrays, and dislocation monopoles using linear elasticity theory and molecular dynamics (MD) simulation. While linear elasticity theory facilitates a quantitative evaluation of the elastic field, it fails to account for out-of-plane deformation of the material. Therefore, MD analysis, which considers out-of-plane deformation, was employed to obtain versatile results applicable to a broader range of materials. Our findings from both theoretical analyses indicate that, in terms of strain–energy, a disclination dipole with a large separation can be represented by a dislocation array, whereas a dipole with a small separation can be represented by a dislocation monopole. This study newly performs strain–energy analysis of dislocations and disclinations using these two theoretical approaches.

Two-Coordinate Dinuclear Donor-Gold(I)-Acceptor Complexes Exhibiting Multiple Excitation Wavelength Dependent Phosphorescence.

Two-coordinate Au(I) complexes with a donor-metal-acceptor (D-M-A) structure have shown rich luminescent properties. However, charge-neutral dinuclear donor-metal-acceptor type Au(I) complexes featuring aurophilic interactions have been seldom explored. Herein, we describe the structures and photoluminescence properties of two dinuclear Au(I) complexes, namely DiAu-Ph and DiAu-Me. Single crystal X-ray structural analysis of DiAu-Ph reveals a short intramolecular Au-Au distance of 3.224 Å. In dilute solution and doped films, excitation wavelength dependent multiple phosphorescence phenomena were observed for these dinuclear complexes. Theoretical calculations reveal that the aurophilic interaction causes increased contribution of the Au d orbital to the highest occupied molecular orbitals. Thus, the gap between singlet and triplet excited states (ΔEST) is enlarged, which disables the thermally activated delayed fluorescence (TADF). Moreover, the large energy separation (0.45-0.52 eV) and the different orbital configurations between the various excited states result in an inefficient internal conversion, accounting for their multiple phosphorescence properties.